The effects of pH value of chloride immersion solution and activator type on chloride solidification capacity of alkali-activated slag （AAS） paste were studied.The hydration products and micro-morphology of AAS before and after immersion in chloride solution were analyzed comparatively based on chloride exposure-equilibrium method and microanalysis methods involving XRD， TGA-DSC and SEM. The physical adsorption and chemical binding in the solidification of chloride by alkali activated slag paste were quantitatively evaluated. The results show that the chloride binding amount of AAS paste decreases with the pH value of immersion solution. The solidification capacity of slag activated by water glass （WAS） is greater than that of slag activated by NaOH（NAS）. The solidification of chloride of alkali activated slag not only includes physical adsorption， but also a small amount of chemical binding. For all three pastes involving NaOH activated slag， water glass activated slag and ordinary Portland cement， the physical adsorption in the solidification of chloride accounts for more than 50%.